It is known in the technical sector relating to the packaging of liquid products and the like that there exists the need to manufacture plastic containers suitable for use with the product which they must contain.
It is also known that said containers are formed in suitable blow-moulding machines provided with associated moulds (composed of two half-moulds movable into open/closed positions) inside which a plastic tube (parison) extruded upstream of the mould is introduced and blow-moulded and that said machines are substantially formed by a plastic tube extrusion unit, a blowing unit, a container holding mould formed by two half-moulds movable, upon operation of associated first means, in a longitudinal direction symmetrically with respect to a fixed axis perpendicular to said longitudinal direction and that the entire unit, formed by the mould and by the associated first operating means, is movable, upon operation of associated second operating means, in a transverse direction, from a first position, corresponding to positioning of the mould below the extrusion unit, into a second position corresponding to positioning of the mould below the blowing unit.
It is also known that, in order to reduce the contamination resulting from the movements performed by oil-hydraulic means and improve the precision and stability of the associated closing movement of the half-moulds, operating systems which use electric motors have been introduced; these systems, although suitable for machines with relatively small dimensions (and therefore with a low mould closing force), are unsuitable for the movement of displacement units in larger size machines where the high masses which must be displaced with very fast accelerating and decelerating movements—needed in order to keep the displacement idle time within the limits permitted by the machine cycle for forming a part—result in a high power consumption which greatly increases the final costs for production of the containers.
Such a machine is for example known from EP 1,591,226 in the name of the same present Applicant.
U.S. Pat. No. 6,526,800 and FR 2,902,366 also disclose known devices generally used in association with machine tools and able to perform recovery of the energy resulting from deceleration of electrically operated moving parts.
Although fulfilling their function, these devices nevertheless have the drawback arising from the fact that also a part of the energy recovered is dissipated owing to the limited efficiency of the recovery apparatus and the poor synchronization of the energy recovery/supply between the operating systems for the various moving parts.